A common practice in the recovery of oil and/or gas from subterranean formations is to treat the formations to increase their gross permeability or conductivity by procedures that are identified generally as fracturing processes. For example, it is a conventional practice to hydraulically fracture an oil or gas well in order to produce and propagate one or more cracks or “fractures” in the surrounding formation by mechanical breakdown of the formation.
Hydraulic fracturing typically is accomplished by injecting a hydraulic fracturing fluid into the well and imposing sufficient pressure on the fracturing fluid to cause the formation to break down with the attendant production of one or more fractures. The fracturing fluid is usually a gel, an emulsion, or a form having a proppant such as sand or other particulate material suspended therein. The proppant is deposited into the fracture and functions to hold the fracture open after the pressure is released and the fracturing fluid is recovered from the well.
After the fracturing fluid has been pumped into the formation and fracturing of the formation has been achieved, it is desirable to remove the fluid from the formation to allow hydrocarbon production through the new fractures. Generally, the removal of the fracturing fluid, which is highly viscous, is realized by “breaking” the gel, emulsion, etc., i.e., by converting the fracturing fluid into a low viscosity fluid.
As oil and gas exploration and production moves into progressively deeper offshore waters, greater challenges are being presented. For example, it is known that gas hydrates pose particular problems with respect to the producing, transporting, and processing of natural gas and petroleum fluids. These gas hydrates, known as clathrate hydrates, are crystalline compounds that form when water forms a cage-like structure around gas molecules, particularly gaseous molecules. Typical gas hydrates formed in petroleum environments are composed of water and one or more gas molecules such as methane, ethane, propane, isobutane, normal butane, nitrogen, carbon dioxide, hydrogen sulfide, etc.
While gas hydrate formation may pose a significant problem during production from a well, it may also pose a problem in a fracturing operation. As noted above, once the fracturing operation has been completed, the fracturing liquid has to be recovered or unloaded before the well commences producing hydrocarbons. In the unloading process, the fracturing fluid is frequently saturated with one or more of the gases mentioned above, which undergo decompression, resulting Joule-Thompson cooling of the fracturing fluid. Accordingly, when the fracturing fluid is water-based, gas hydrates may form at certain well depths, plugging the well and interfering with the process of bringing the well onstream. Therefore, there is a need for a well service composition and method for controlling or minimizing the formation of gas hydrates.